Following the deaths of at least 16 endangered North Atlantic right whales this year in Canadian and U.S. waters, a new study has confirmed what scientists already suspected — their habitat range has shifted.
After the whales started disappearing from the Scotian Shelf off southern Nova Scotia and other areas where they were common, scientists began pulling together data gathered from underwater microphones mounted to the ocean floor.
"We had 19 different organizations that had passive acoustic data collected for various purposes from 2004 to 2014," Genevieve Davis, a researcher at the Northeast Fisheries Science Center in Woods Hole, Mass., told CBC's Information Morning.
The microphones had gathered the sound of right whale "up-calls," a distinctive whooping that ascends from low to high and which allows the whales to stay in contact with others throughout their range.
"We can identify when they're in the area by finding these up-calls, so that's how we go through the sound data," said Davis, who is a lead author of the new study, which is published in the journal Nature Scientific Reports. "We look at it through spectrograms, which are a visual display of sound, and we can pick them out that way."
The study showed a transition after 2010 away from the usual habitats, such as the Bay of Fundy and northern Gulf of Maine. The whales are instead spending more time in the mid-Atlantic region and the Gulf of St Lawrence.
Twelve right whales have turned up dead this year in the Gulf of St. Lawrence. Necropies on seven showed four likely died after being hit by ships, and two were likely killed after becoming tangled in fishing lines.
The whales' appearance in the gulf — possibly as a result of warming ocean temperatures and changing prey behaviour — is surprising, Davis said.
"Part of the issue is we haven't really monitored that area to the same effect," she said. "They could have been using that habitat, just maybe not as much or to the same amount as they have now."
Ship strikes and entanglements
Davis said confirmation of the whales' changing migration patterns can help policy makers decide where to concentrate further monitoring efforts, and when to take steps like halting fishing or slowing shipping traffic.
"Ship strikes and entanglements are the issue, full stop," she said.
Davis said the Canadian government's efforts in the Gulf of St Lawrence, including vessel speed restrictions imposed in August, are a positive step. However, the breadth of the whales' range suggests that limiting mitigation measures to small areas won't be enough of a safeguard.
In addition to tracking the ways in which right whale habitat has changed, the study also shows just how far-reaching that habitat is.
"One of the main things is it's showing just how much whales move in general throughout the year," she said.